There are presently available on the market place various devices and apparatuses for electrically testing an individual light bulb after it has been physically removed from its socket. Apparatus is also available on the market for testing Christmas tree light bulbs by physically placing an alternating current line voltage sensor in close proximity to the particular light bulb desired to be tested. However, such a device is merely an electromagnetic field strength detection device which many remain in an “on” condition whenever the particular Christmas tree light bulb desired to be tested is physically located in close proximity to another light bulb or bulbs on the Christmas tree.
Light bulb manufacturers have also attempted to solve the problem of bad bulb detection by designing each light bulb in the string in a manner, whereby the filament in each light bulb is shorted whenever it burns out for any reason, thereby preventing an open circuit condition to be present in the socket of the burned-out bulb. However, in actual practice, it has been found that such short circuiting feature within the bulb does not always operate in the manner intended and the entire string will go out whenever a single bulb burns out.
U.S. Pat. No. 6,765,313, by the present inventor, discloses and claims a circuit which solves the problem of the entire series wired string of lights going out as a direct result of either a defective socket, a light bulb being improperly placed in the socket, a broken or bent wire of a light bulb, or whenever a light bulb is either intentionally removed from its socket or is merely dislodged from its socket during handling or from movement after being strung on the Christmas tree, particularly in outdoor installations subject to wind or other climatic conditions. U.S. Pat. No. 6,765,313 teaches a novel filament shunting circuit for use in connection with a series connected string of incandescent light bulbs which completely overcomes, in a very simple, novel and economical manner, the problems associated with prior arrangements which were primarily designed to maintain some sort of current flow through the entire string of bulbs whenever one or more bulbs in the string becomes inoperable, either due to an open filament, one or more faulty bulbs, one or more faulty sockets, or simply because one or more of the bulbs are not properly mounted in their respective sockets, or are entirely removed or fall from their respective sockets.
More specifically, in accordance with the circuit of U.S. Pat. No. 6,765,313, the disclosure of which is incorporated herein in its entirety, a silicon type shunting device, preferably a Zener diode, is connected across each light bulb of the series wired light string, the Zener diode having a predetermined voltage switching value which is greater than the voltage normally applied to said bulbs, and which Zener diode shunt becomes fully conductive only when the peak voltage thereacross exceeds its said predetermined voltage switching value, which occurs whenever a bulb in the string either becomes inoperable due to any one or more or all of the following reasons: an open filament, faulty or damaged bulb, faulty socket, or simply because the bulb is not properly mounted in its respective socket, or is entirely removed or falls from its respective socket, and which circuit arrangement provides for the continued flow of rated current through all of the remaining bulbs in the string, together with substantially unchanged illumination in light output from any of those remaining operative in the string even though a substantial number of total bulbs in the string are simultaneously inoperative for any combinations of the various reasons heretofore stated.
The circuit arrangement of U.S. Pat. No. 6,765,313 includes a full bridge rectifier disposed between the AC power supply and the series wired light string to provide pulsating DC power to the light string.